| The N-terminal coiled-coil(CC)domain peptide N21 can induce tobacco hypersensitive response(HR),which is an important functional structural unit of harpin protein,which is produced by the rice blight bacterial pathogen Xanthomonas oryzae pv.oryzae(Xoo).Therefore,the further study of the application of the peptide N21 in plants and its mechanism will help to understand harpin protein and application of these proteins or peptides.In this study,peptide N21 was applied in vitro to study the effects of growth-promoting,disease resistance and drought resistance.Using tobacco cDNA microarray,this paper determined the transcriptional profiles of transgenic N21 gene tobacco plants under drought stress and TMV stress.The differential expressed genes related to different signaling transduction pathways and defense response were analyzed by paired comparison to understand the molecular mechanism of N21 eliciting beneficial traits.N21 peptide can significantly promote plant growth.When plants were treated with N21 peptide(40 p,g/mL),the plant height of tomatoe,pepper,cucumber,melon and wheat was increased by 12.35%,29.43%,20.94%,7.00%and 12.42%,respectively,compared with the control.The root length of these plant were increased by 11.70%,24.80%,51.42%,11.72%and 4.88%compared with the control,and the number of tiller and leaf of the treated plants were also significantly higher than those of the control.N21 polypeptides can also improve plant disease resistance.Experiments in vitro showed that peptide N21 could obviously put off the occurrence of tomato gray mold,strawberry gray mold and peach brown rot,and reduce these disease severity,and the control effects were 80%,80%,and 75%,respectively,which were equal to chemical fungicide carbendazim.N21 polypeptide could also enhance the drought resistance of plants.After 2 days of tobacco drought stress(PEG),most of the leaves of the control group showed obvious irreversible wilting symptoms,while the N21 spraying tobacco plants grew normally,with slight wilting symptoms of a few lower leaves.These results indicated that the application of peptide N21 in vitro could promote growth,disease resistance and drought resistance.The data of six pairs of transcripts of transgenic N21 gene and non-transgenic parental tobacco(CK)under TMV and drought stress(PEG)were compared and analyzed by the standard of three-fold(ratio>3.0 or ratio<0.33)differential expression difference(ratio>3.0 or ratio<0.33).When transgenic N21 tobacco inoculated by TMV compared with transgenic N21 tobacco[N21(TMV)and N21],there were 1813 genes were up-regulated and 1840 genes were down-regulated.Contrasting transgenic N21 tobacco inoculated by TMV compared with parental tobacco inoculated by TMV[N21(TMV)and CK(TMV)],928 genes were up-regulated and 895 genes were down-regulated.Compared with parental tobacco(CK),parental tobacco treated with PEG had 1704 up-regulated genes and 2817 down-regulated genes.Compared N21(PEG)and N21,there were 2019 up-regulated genes and 2763 down-regulated genes.In N21(PEG)and CK(PEG)comparison,there were 517 up-regulated genes and 565 down-regulated genes.The disease resistance related genes of differential expression between CK(TMV)and CK,N21(TMV)and N21,N21(TMV)vs and CK(TMV),were further analyzed.(1)TMV-treated parental tobacco compared to parental tobacco,there were 120 differentially expressed genes related to disease resistance,and in which 48 genes were up-regulated and 72 genes were down-regulated.There were 29 differentially expressed genes associated with ABA signaling pathway,35 genes associated with JA signaling pathway,13 genes in ethylene signaling pathway,8 genes associated with SA signaling pathway,6 genes involved in calcium signal regulation,and 6 genes related to PR protein.(2)There were 82 differentially expressed genes related to TMV-inoculated transgenic N21 tobacco compared with transgenic N21 tobacco.Among them,49 genes were up-regulated and 33 genes were down-regulated.In which,there were 17 ABA-related genes,27 JA-related genes,10 ET-related genes,3 SA-related differentially expressed genes,respectively,and 23 genes associated with calcium signaling regulation and 3 PR-related genes.(3)Comparing TMV-inoculated transgenic N21 tobacco with TMV-inoculated parental tobacco,a total of 39 differentially expressed genes were identified,with 23 up-regulated and 16 down-regulated genes.The differentially expressed gene numbers associated with ABA,JA,ET,SA,calcium signaling pathway and PR mode were 3,12,11,2,8 and 3.In addition,some differentially expressed genes were also identified by qRT-PCR. |
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